Hi frisgul,
With the exception of Makehuman, the other programs you listed create base models with far too many polygons to be very useful in games IMO, requiring retopology/low poly conversion work (/Poser might have a lower poly option for an additional fee - someone else can probably tell you more). If you just need human bodies on the cheap, I’d say stick with MH, which is more than capable.
To attach a custom head, as well as model your own custom clothing/armor/hair/etc., you’ll need some proficiency with at least one of the popular 3D programs like Blender (which is very MH friendly), 3dsMax, Maya, Modo, Studio, etc. Max and Maya have the smoothest pipeline to UE4 right now through FBX 2013/2014. Some serious progress is being made in regard to Blender’s pipeline to UE4 as well, but I’m not quite up to speed with that.
If you’re using Makehuman’s pre-rigged models, then Maya (which can use Epic’s character tool), Blender, IKinema, Motionbuilder, 3dsMax, or any other animation friendly program should help you to create your own animations (they can also import motion capture animations for you to tweak). For automatic rigging (skeleton creation and placement) and skinning (attaching the skeleton to your model, usually using weights), Mixamo is pretty awesome as mentioned above, although there is a cost per model (if I understand their pricing chart correctly, you get two free auto-rigs, after which the cost is $79 per model). You can do the rigging and skinning manually in the programs listed above, but it definitely takes some time to !
Good luck!
-T